We propose to study the metabolism of pulmonary surfactant lecithin, as well as of pulmonary and hepatic lecithins using both in vivo and in vitro systems. For both short term studies of synthetic rates and long term studies of turnover metabolic rates will be followed with the use of isotopic tracers of 2-H3-glycerol, 1-C14-palmitate, 1-2-C14-choline, H3-betaine, and P32-phosphate. Water soluble precursor of lecithins will be isolated, and their pool size and specific activities determined at various times. Computer methods will be used to fit data to metabolic schemes. The effects of exposure of animals to atmospheric pollutants such as cigarette smoke, ozone, SO2 and NO2 upon the metabolism of these lecithins will be investigated.